Process of producing well-clouded enamels or glazes by means of substitutes for stannic oxid.



HEINRICH KRETZEB, OF WALLERSHEI'EI, NEAR COBLENZ, AND

COBLENZ, GERMANY; SAID CAPPEL ASSIG'NOB TO SAD} KREELEEFV.

PROCESS OF PRODUCING WELL-CLOUDED EN lJEJIEIIS TU'IES FDR STANNIG if)? 113.

No Drawing.

To (ZZZ whom it may concern:

Be it known that We, HEINRICH KRETZER, doctor of chemistry, residing at lVallershelm, near Coblenz, and AUGUST CArPnL, chemical engineer, residing at Coblenz, Germany, have invented certain new and useful Improvements in Processes of Producing VVell-Clouded Enamels or Glazes by Means of Substitutes for Stannie OXid, of which the following is a specification.

As it is known, in modern, enameling practice stannic oXid as Well as the other specifying substances proposed in substitution are used in such a Way that they are added to the comminuted enamel proper When being ground in the Wet-mill and that this mixture is subjected to the Wet grinding operation until the enamel has been very finely ground-a condition nec essary to laying-on the enamel. This Wet grinding operation generally continues for from five to ten hours.

If treated in this Way most of the opacifiers other than stannic oxid, employed in the manner described above and in quantities corresponding to the amount of stannic oXid commonly used, yield clouding efl ects totally insuificient. However, if used in larger quantities they Will produce injurious secondary phenomena or the process will become so expensive that an advantage Worth mentioning will not arise over the use of stannic oXid.

Up to now it Was generally believed that this deficiency of opacifying power was due to the nature of the products themselves. Therefore, various proposals were made for removing this drawback by slightly modifying their chemical composition, however Without any remarkable success. Applicants experiments v uh these substitute opacifiers proved that the intensity of the clouding or opacifying effect of any of the substances mentioned is by no means the same With different enamels, but that it may vary Within Wide bounds. Moreover applicants have stated that the same clouding agent used in the manner described above may produce different opacities with the same enamel.

Now applicants have found that most of the enamels When being subjected to the Wet grinding operation together with the opacifying agents have a decided tendency Specification of Letters Fatent.

Application filed. September 9, 19142.

llatent-ed Sept. a, Serial No. 869.838.

to affect these substances and to transform them into soluble forms (for instance by hydration, dispersion, formation of colloids, etc). Contrary to stannic oxid w i not or only very slightly affected by the Wet-milling process, these agents will their clouding or covering power in same measure as their alteration by the urn milling process, that is to say, to the that the formation of soluble or irmabl'e colloidal, etc, proceeds.

()n the other side it has been found that the opacifying power of these substitute substances will not be diminished if all injurious influences during the wet milling process are removed. This may be etlect by avoiding or at least reducing the dill-,1" tion of the Wet milling operation after having introduced the clouding agents in ues tion or by adding such substances to the enamel paste which in the Wet milling opera ticnl will impede a colloidal transforma tion of the opacit'ying substance. i s al ready mentioned staunic oxid does not su such injurious alterations, le' st not in the measure as those substitute op; iifiers which contain Zirconium, titanium, silicon, aluminum, Zinc, alkaline metals, earth alkaline earth metals or compounds same.

ever, according to the invention, which is the subject of the application, it is possible U to obtain norm and quite satisfying enamels with the substitute clouding agents m. 'ntioncd.

In practice, this result is attained by ing to subject the opaci'fiers. mentioned, it was the custom up to now, to the We mill g process during the same time a the enamel proper, but by adding same only after the enamel proper has undergone the Wet milling process for the greatest part, that is to say after the enamel has alrcz-uly got a line and pasty condition.

he same result, although in a smaller measiue is accomplishml by introducing into the mill at the same time with the opacifying agents such substances which countcract to a transformation of the opecifiers into the colloidal or sol state, such as clcctropy' a (for instance chlorid of ammonium,

fail

sulfate or chlorid of magnesium, sulfate of sodium, etc), as Well as flocculating or precipitating colloids or similarly acting sub stances. From this point of View it pears also disadvantageous to let the finished milled enamel paste to settle any longer time as it has been proposed.

Finally it is to be remarked that antimonic products, for instance oXid of antimony, metaantimoniate of sodium, etc., act in a manner similar to stannic oxid regarding their being not altered in the wet mill. However, as it is known, antimonic compounds when used for enamel clouding purposes show the drawback that the enamel paste becomes slimy and is only with great difficulty to be laid on. For-th re sin heretofore only small quantities of anti- .monic opacifiers (4; to 5 per cent.) could be added to the enamel paste. \Ve have found that the quantity of such antimonic opacifiers could be increased (twice, or more) and added to the enamels proper without the mentioned injuries being observed, if it is omitted to have these opaquing substances undergo the whole wet-milling operation together with the enamel proper, or if such substances as will counteract the formation of sols be added to the mass in the mill.

e claim as our invention 1. In the manufacture of white clouded enamels or glazes by means of opacifiers other than stannic oxid, the improvement which consists in adding the opacifying agents to the enamel proper when being ground in thewet mill only after the milling process has been accomplished for the greater part.

2. In the manufacture of white clouded enamels or glazes by means of opacifiers other than stannic oxid, the improvement which consists in adding to the enamel proper when being ground in the wet mill, the opacifying agents together with such substances as will counteract a transformation of the 'opacifiers into colloidal forms.

3. In the manufacture of white clouded enamels or glazes by means of opacifiers other than stannic oxid, the improvement which consists in adding tothe enamel proper when being ground in the wet'mill, the opacifying agents together with substances acting as electrolytes.

4. In the manufacture of white clouded enamels or glazes by -means of opacifiers other than stannic oxid, the improvement which consists in adding to the enamel proper when being ground in the wet mill, the opaeifying agents together with substances acting as precipitating colloids.

HEINRICH KRETZER. AUGUST CAPPEL.

Witnesses:

A. H. SoHnoDER, Fl N. SEELEY. 

